Signal system



R. A. HEISING May 7, 1929.

SIGNAL SYSTEM Original Filed May '16, 1924 //v VENTUR. 5 Rama/v0 A. HE/S/NG' %fiM Arm/m5) Patented May 7, 1929.

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISING, OF MILLBUR-N, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SIGNAL SYSTEM.

Original application filed May 16, 1924, Serial No. 713,694, Patent No. 1,664,860, dated April 3, 1928. Divided and this application filedFebruary 28, 1928. Serial No. 257,614.

This invention relatesbroadly to signaling, and more particularly to a terminal circuit of a multiplex two-way transmission and receiving system for radio communication, the application being a division of application Serial No. 713,694, filed May 16, 1924, Patent No. 1,664,860, patented April 3, 1928.

The objects of the invention are to provide 7 for the operation of several simultaneous twoway communications over a radio link, using a single antenna or other radiating.structure at each terminal station, and to do this with a minimum of interference between the twoway channels employed for such communications and between the transmitting and receiving portions of each two-way channel.

Ina specific embodiment of the invention the several two-way terminal circuits are connected to individual branches of an antenna having a common aerial portion, such aerial portion and each branch being together separately resonant at the frequencies of both the transmitted and the received waves corresponding to the two-way channel connected to that branch. Each branch also includes antiresonant circuits equal in number to the remaining two-way channels, for preventing interference therefrom. The anti-resonant circuits, therefore, make each branch, which is individual to a two-way channel in combination with the aerial portion, functionally independent-of each of the other similar combinations of individual branch and common aerial portions.

Anti-resonant means may also be included in the receiving portion of each two-way channel associated with an antenna branch for preventing interference between the transmitting and receiving portions of each such channel. Alternatively, the relation between the transmitting and receiving portions of each channel may be such as to make pos sible the utilization of the transmitting frequency to combine with the incoming signal wave and thereby step down its frequency, as in well known types of plural detection receiving systems. 1

The invention will be more clearly understood by reference to the following specification and the accompanying drawings in which the single figure shows a circuit arrangement for a plurality of two 'way multi-,

plex channels operating in connection with the same antenna.

' Referring to the drawing, three channels have been shown at 1, 2 and 3. Each channel includes circuits for screening it against interference from adjacent channels, while permitting transmission and reception of energy in the particular channel in which the screen ing means may be located. 6

Channel 1 is divided into a transmitting circuit 4 and a receiving circuit 5. Thetrans mission system connected to the transmission circuit 8 may include a source of sustained oscillations designated 6 connected to impress energy of constant frequencv upon a modulation circuit including electron tube 7 The high frequency oscillations from the source 6 may be modulated at voice frequency from a circuit represented at 8 and the modulated high frequency oscillations are impressed upon the amplification system 9. This system operates to increase the amplitude of the energy to be transmitted and to deliver the amplified energy to the radiating antenna system, comprising antenna 10, in-

ductance 11, capacity 12 and ground 13.

Circuits consisting of inductance 14 shunted by capacity 15, and inductance 16 shunted by capacity 17 are provided in the antenna connection for the purpose of screening the communication channel from reaction or disturbance of oscillations produced in adjacen channels as will be hereinafter described.

The receiving system of channel 1 includes a circuit consisting of inductance 18 and shunt capacity 19 which isclosely resonant'to the frequency of the source 6 of the transmitting circuit 4, but can be detuned from that frequency sufiiciently to permit a desired amount of energy from the local transmitting channel to flow in the receiving circuit. This energy is used in cooperation with the incoming signal energy for the production of a beat note. enabling the signals to be observed. 1 The receiving circuit 5 includes the primary antenna inductance 20 and tuning condenser 21 connected to ground 22. The frequency derived from the inter-action of the incoming signal energy with the energy from the local transmitting source may be combined in the detector tube 23 to produce a beat frequency wave andthe beat frequency Wave is impressed upon a detector circuit including tube 24 which operates to reproduce the signal transmitted from the distant station.

The second duplex channel represented by connection 2 with the antenna has circuits interposed between the transmitting and receiving apparatus and the antenna system designed to eliminate the passage of undesired disturbances or reactions from the associated channels into the transmitting or receiving apparatus of the channel 2. These circuits include inductances 25 and 26 shunted by con densers 27 and 28, respectively.

The transmitter for this channel is represented as having a source of sustained. oscillations 29 connected with suitable modulation and amplification circuits represented generally at 30. The oscillations to be transmitted are modulated at voice frequencies through circuit 31. The transmitting energy is delivered to the antenna system through inductance 32 connected in the antenna and ground circuit in series with condenser 33.

In the lead from the antenna 10 through connection 2 to the receiving apparatus in this channel there is interposed a circuit including an inductance 34- shunted by condenser 35 to constitute a circuit tuned to exclude oscillations supplied by the local source 29 to the associated transmitter circuit.

The receiver energy is impressed upon the receiving circuit through primary inductance 36 shunted by tuning condenser 37. A local source of oscillations may be supplied by means of a local generator 38 coupled with the secondary winding 39 through an inductance 40.

An electron tube 41 is connected to function as a detector which operates to reduce the he quency of the incoming signal wave to an intermediate frequency determined by the frequency of the source 38. The intermediate frequency wave is amplified by amplifier 42 and selectively impressed upon another detector 43 through a series of selective circuits or filter 44. The signal produced by the detector 43 is applied to responsive device 45. The frequency of source 33 is fixed with respect to the i coming wave to produce a wave of intermediate frequency which should be different from that produced by combining the incoming signal. wave with the transmitted wave for this channel. The intermediate frequency wave should preferably have a frequency different from that produced by combining the incoming signal wave with any of the waves used in the other channels.

Channel 3 is connected with the antenna 10 through a lead having circuits interposed therein for excluding wave frequencies used in the associated channels. The circuits for doing this comprise inductances 46 and 47 shunted by condensers l8 and 4-9 respectively.

The transmitting circuit 50 of channel 3 may be provided with a local carrier source of oscillations designated as having a frequency F, the energy from which is modulated by a signal in'the manner described with reference to transmitting channels 1 and 2. The signal modulated wave is impressed on the antenna circuit through the inductive coupling 51. v

The receiving system for the channel includes a circuit in series therewith comprising inductance 52 and condenser 53 which functions to exclude from the receiving system the oscillations supplied to the transmitting eircuit. It may function as in channel 1 to permit a desired amount of the locally transmitted energy to flow to the receiving circuit. The receiver may be coupled to the system by the winding 54 inductively associated with the winding 55. Condensers 56 and 5'? are used to assist in tuning the coupled circuits to the desired frequency.

It will be observed that means are provided in each of the several channels for supprcss- 7 ing reactions and interference from currents occurring simultaneously in the other channels. In channel 1, circuits 14, 15 and 16, 1'? will suppress undesired oscillations or currents which might be impressed upon channel 1 by reason of the flow of energy proper to channels 2 or 3.

The circuit 18, 19, in the receiving portion of channel 1, excludes from the receiving circuit all energy excepta desired amount, derived from the outgoing carrier wave supplied by the oscillator 6 for outgoing transmission over channel 1, which may be utilized in reception. V

. In channel 2, the circuits 25, 27and 26, 28' exclude undesired currents which may be supplied from channel 1 or 3. The circuit 34, in channel 2 prevents too great reaction of the sustained wave supplied for transmission by generator 29, upon the receiving portion of the channel. i

In channel 3 the circuits 46, 48 and 47, 49 exclude undesired currents which may be supplied from channels 1 and 2, while the circuit 52, 53, in the receiving portion of the channel, operates to prevent undesired reaction of the sustained wave fromeireuit 50 in such receiving portion of the channel.

All of the channels may, therefore, function in duplex operation in multiplex signaling on the same antenna 10 without mutual reaction or cross-talk.

The incoming signaling energy in the antenna system 10 distributes to the several receiving portions without interference since these receiving portions are respectively selective to their individual message waves.

For the purpose of clearly explaining the operation of the system, the transmitting frequency in duplex channel 1 may be assumed 1 to have a value equal to f,. The ineomingsignaling energy in antenna 10 selected by channel 1 may have a frequency f A portion of the transmitting frequency f, being effectively utilized in the receiving portion of channel 1, as a local source of oscillations, re-.

be employed. The beat frequency thus derived will be f, f =f which may be detected in device 43 to enable the signals to be observed. Similarly the channel 3 may have a transmitting wave of frequency f, and the incoming frequency in antenna 10 for this channel may be f A portion of the transmitting frequency f may be utilized as a local source, so that the beat frequency produced by thereceiver will be The beat frequency 7, may be detected and the signal indicated.

While the invention has been described in certain particular embodiments, it should be understood that modifications may be made and that the invention is not limited except by the scope of the appended claims.

What is claimed is:

1. A multiplex radio communication system comprising in combination a single aerial antenna, a plurality of duplex units, each ineluding a transmission channel and a receiving channel connected between said antenna and ground, each duplex unit employing different frequencies from all of the others, the receiving frequency of each duplex unit being different from the transmitting frequency of the same unit, means interposed between said antenna and each of said duplex units for preventing interference from currents occurring simultaneously in said other units, and means comprising a loop tuned circuit interposed in the receiving portion of each of said units for preventing interference due to current flow in the transmitter channel.

2. A multiplex radio communication system comprising in combination a single antenna structure, a plurality of connections between said antenna structure and each of a plurality of duplex communication channels, each comprising transmitter and receiver portions, each duplex unit employing different frequencies from all of the others, the receiving frequency of each duplex unit being different from the transmitting frequency of the same unit, means comprising a succession of loop tuned circuits interposed in each of said connections capable of passing currents of the frequencies used for transmitting and receiving by the respective duplex channels but preventing interference in each of said channels from currents existing simultaneously in said other channels, and separate means comprising a loop tuned circuit connected in each of said receiver portions for screening the receiver from undesired effects of the adjacent transmitter portion.

3. A multiplex radio communication system comprising, in combination, an antenna having a common aerial portion and a plurality of branches, a plurality of duplex channels, each comprising a transmitting and a receiving portion, and each such channel connected in energy transfer relation to an individual one of said branches, and a plurality of means in each of said branches, each such means being selective at. a frequency individual to the transmitting frequency of one of the other channels, for preventing interference from currentsoccurring simultaneously in said other channels, the transmitting and receiving apparatus of each duplex channel employing frequencies sufficiently different to permit them to be separated by selective circuit s, said frequencies being closer together in the frequency spectrum than any two frequencies used by different duplex channels, whereby said plurality of means in each channel is capable of passing all of the frequencies used by the respective portions of the duplex channel in transmitting and receiving, while efiectively excluding currents. of frequencies used by the other channels of the system.

4. A multiplex radio communication system, comprising in combination a single earthed antenna, a plurality of duplex units, each including a transmission channel and a receiving channel connected between said antenna and-the ground, each duplex unit employing different frequencies from all of the others, the receiving frequency of each duplex unit being different from the transmitting frequency of the same unit, means interposed between said antenna and each of said duplex units for preventing interference caused by currents occurring simultaneously in said other units, and means comprising a loop tuned circuit interposed in the receiver portion'of each of said units for preventing interference caused by current flowing in the transmitter portion.

5. A multiplex radio communication system, comprising in combination a single antenna structure, a plurality of connections between said antenna structure and each of a plurality of duplex communication channels, each comprising transmitter and receiver portions, each duplex unit employing different frequencies from all of the others, the receiving frequency of each duplex unit being different from the transmitting frequency of the same unit, means comprising a succession of looped tuned circuits interposed in each of said connections capable of passing currents of the frequencies used for transmitting and receiving by the respective duplex channels but preventing interference in each of said channels due to currents existing simultaneously in said other channels, and separate means comprising a loop tuned circuit connected in each of said receiver portions for screening the receiver from undesired efiects of the adjacent transmitter portion.

6. In a multiplex signaling system a two- Way transmitting circuit, a plurality of two- Way circuit branches connected thereto, fre-.

quency selective means included in each of said branches for selectively passing frequencies employed by the branch, While 6X- eluding frequencies employed by the other branches, a pair of oppositely directed one- Way paths connected to each two-Way branch and employing different frequencies for transmitting and receiving, a frequency selective means comprising a loop tuned circuit in each one-Way receiving branch for permitting the passage of Waves employed for receivlng While reducing to an unob]ectionable amount the frequencies used by the transmitting pathconnected to the same two- Way branch.

7 A multiplex system according to claim 6 in Which a source of continuous Waves is associated with the transmitting path connected to each tWo-Waybranch, said Waves being separated in frequency from the frequency employed for receiving from the same two-way circuitbranch by a, superaudible frequency which is small compared with the frequency separation between two Waves used by different similarly directed one-Way branches, means in a receiving path for combining incoming Waves With the,

Waves from the said source in the transmitting path connected to the same two-Way branch for producing a super-audible beat Wave, and means in the receiving path for detecting said heat Wave. 7

In Witness whereof, I hereunto subscribe my name this 24th day of February, 1928.

RAYMOND A. HEISING, 

